Global climate regulation (Carbon storage in biomass)
Description​
Plants absorb carbon from the environment and use it to build biomass. The carbon is therefore (temporarily) removed from the environment. All nature types absorb carbon, but forests with a large, long-lived biomass are especially important for absorption. In other nature types, this absorption of carbon is more temporary, because the carbon is returned to the environment when the plants decay. The carbon that is captured in the biomass of forests can no longer contribute to warming our climate.
The method for carbon storage in biomass is closely related to wood production and has been developed by Ghent University, Department of Forest and Water Management, Lab for Forest & Nature (Prof. Kris Verheyen).
Required information:
- Number of hectares of forest, divided by tree species
- Soil texture, drainage class and profile development of the forest soil can be found in the information sheet on the soil map of Flanders (https://dov.vlaanderen.be/page/bodemkaarten).
Qualitative valuation​
The qualitative score for carbon storage is the same as for wood production. The score indicates the suitability of a specific soil for a specific tree species. How this is translated into m³ growth depends on the type of tree species. This means that the score and the m³ increase are not always in the same ratio. This also has consequences for C storage in biomass.
Quantitative valuation​
The quantification of the carbon storage in living biomass is done on the basis of the maximum average annual growth of spindle wood (Iv) as listed in the wood production service. To calculate the annual carbon storage, the growth of branches and roots is first estimated and added to the growth of spindle wood. The so-called Biomass Expansion Factors (BEF) are used for this purpose. Subsequently, the growth in m³ per ha per year is converted into carbon (C) per ha per year by means of: the species-specific carbon density (expressed as tonnes C/m³) (density factor x carbon conversion factor of 0.5). This leads to the following formula (Vande Walle et al. 2005): C sequestration (tonnes of C per ha per year) = IV x BEF x C density. The formula used is originally intended to determine the carbon stocks and assumes that the biomass growth is allocated in proportion to the biomass of the tree compartments (trunk, branches and roots).
Table: average density (ton/m³) and biomass expansion factor (BEF) of the tree species distinguished in SIM4Tree (excerpt)
| Tree species | Density factor (ton/m³) | Biomass expansion factor (BEF) |
|---|---|---|
| American oak | 0.60 | 1.32 |
| Birch | 0.51 | 1.32 |
| Beech | 0.56 | 1.34 |
Source: Borremans et al. 2014
Monetary valuation​
To value carbon storage monetarily, we use key figures from De Nocker et al. 2010. These numbers are based on the method of avoided reduction costs: if more carbon is stored in nature reserves, emission reduction costs can be avoided in other places in order to achieve the given environmental objectives. These key figures are based on the costs of emission reduction measures necessary to ensure that the global average temperature only increases by a maximum of 2°C compared to pre-industrial levels (1780). The figures are derived from a meta-analysis of results from various climate model studies (Kuik et al, 2009).
A point of attention is that new and more expensive measures must be continuously taken to remain on an emissions path that is consistent with the 2°C target. The marginal costs increase over time and range from 20 euros/ton CO2-eq. in 2010 to 220 euro/ton CO2-eq. in 2050 (see table)
Assumptions​
For this method we start from the quantification of wood production. The most important species are discussed. For safety reasons, the figures for mixed deciduous or coniferous wood are used as an alternative to unknown tree species.
Numbers to use​
The figures from the above paragraphs, just as for wood production, can be combined into look-up tables on the website of the Nature Value Explorer. A qualitative score, quantity and monetary value can be derived for each combination of the soil core series (a combination of soil texture, drainage class and profile development of the soil), tree species and management. Unlike wood production, the value here does not depend on the amount of wood actually harvested.
Table: for a specific soil core series to be used for qualitative and quantitative assessment of C storage biomass
| Tree species | Dutch name | Soil-core series | Qualitative | Quantity C storage low operating time (ton C/ha.year) | Quantity of C storage high operating time (tonnes/ha.year) |
|---|---|---|---|---|---|
| 2 | beech | AAx | 2 | 0.7 | 0.5 |
| 2 | beech | Aba | 10 | 1.4 | 0.8 |
| 2 | beech | AbB | 10 | 1.4 | 0.8 |
| 2 | beech | ABC | 8 | 1.2 | 0.7 |
| 2 | beech | Abp | 10 | 1.4 | 0.8 |
| 2 | beech | Abx | 10 | 1.4 | 0.8 |
The score indicates the suitability of a specific soil for a specific tree species. How this is translated into m³ growth depends on the type of tree species. This means that the score and the m³ increase are not always in the same ratio. This also has consequences for C storage in biomass.
Table: monetary valuation: series of key figures for external costs of greenhouse gases for C storage in the period 2010-2050.
| Ref year (1) | euro/ton CO2-eq. | euro/ton C (2) |
|---|---|---|
| 2010 | 20 | 73 |
| 2020 | 60 | 220 |
| 2030 | 100 | 366 |
| 2040 | 160 | 586 |
| 2050 | 220 | 805 |
(1) Ref year = year of emission or storage of greenhouse gas (2) 1 ton C = 3.66 ton C02 Source: based on De Nocker et al. 2010
For intermediate years, the key figures are interpolated linearly. After 2050, the value in 2050 applies. We calculate as standard in the web tool with a range of €100 to €366.
Translation to an indicator​
To report the service, we use 3 indicators for which we add up the ecosystem services carbon storage in the soil and carbon storage in biomass:
- The costs avoided for measures to mitigate carbon emissions. This is equal to the sum of the average monetary valuation of the carbon storage service in the soil and the carbon storage service in biomass.
- The annual carbon emissions of an average Flemish person: 3.55 tons/year
- The carbon emissions of an average car km: 48 g/km (COPERT)
An example​
For the example, we refer to the Dutch version of the manual.